The present invention relates generally to a motor vehicle construction, and more particularly to a mechanical changing system for containers or other detachable superstructures of motor vehicles, such as trucks, trailers or semitrailers.
It is already known to provide such motor vehicle constructions wherein a chassis frame is mounted on the vehicle and a base frame which carries a superstructure, such as a container, a truck or trailer body or the like, is provided with legs which can be folded from an upper retracted orientation to an upright orientation in which they are capable of supporting the base frame on the ground. The base frame is normally carried resting on top of the chassis frame when the base frame and superstructure are to be transported; however, when the base frame and superstructure are to be deposited somewhere, for example for loading or unloading, its legs are folded to upright position so that they can support the base frame and superstructure on the ground and the vehicle with the chassis frame thereon drives off, so that the chassis frame moves out from beneath the base frame and the vehicle can be used for other purposes, serviced, parked elsewhere, or the like.
Conventionally, the chassis frame is connected with the base frame carrying the container or other superstructure, by way of locking mechanisms which are released when the two frames are to be connected. The supporting legs of the base frame are mounted on bearing members which can be pulled laterally outwardly from the base frame before the supporting legs are folded down to upright position. Before folding can be accomplished, snap latches for the individual supporting legs, which have articulated lever supports are manually unlocked to permit the supports to pivot through between 10.degree.-30.degree. in the direction of the rear end of the base frame and to permit the legs to be moved to upright position. The length of the legs is adjustable, an operation which is carried out before they are fully moved to the upright position, i.e. after they have been pivoted through 10.degree.-30.degree.; thereafter they are further pivoted until they extend vertically. The simplest way of effecting the further pivoting is for the vehicle to be driven a very short distance in reverse, which causes the legs whose lower base plates have already been placed into light engagement with the ground, to be moved to fully upright position and to raise the base frame and container or superstructure on it by a corresponding amount. When the legs are in the fully upright position, locking devices automatically engage and latch them in this position. The vehicle can now be driven out from beneath the base frame.
For the reverse operation, namely in order to re-connect the base frame with the chassis frame, the vehicle is backed beneath the base frame until stopping blocks provided at the front end of the chassis frame come to rest against the front edge of the base frame. The two frames are then interlocked and the latching arrangements for the supporting legs are unlocked and as the vehicle subsequently is driven forwardly the legs pivot upwardly and the base frame, which is already loosely connected with the chassis frame, becomes lowered onto the latter. The legs are then folded to their fully retracted position, usually by first telescoping them together and then folding them upwardly, and their supporting members are pushed laterally beneath the base frame.
This prior-art approach has the great advantage that the disconnecting and connecting process is effected solely by mechanical means. Additional hydraulic or pneumatic devices are not at all required, and this results in savings in terms of production and maintenance costs, and also in respect of the unloaded weight of the vehicle so that the useful load factor for the vehicle is correspondingly increased.
It has, however, been found advantageous to have the stopping blocks provided on the chassis frame. These blocks must be relatively tall in order to reliably prevent the base frame or its container or superstructure from striking against the driver's cabin of the vehicle. It must be noted in this connection that the vehicle, when relieved of the base frame, is spaced quite a significant distance from the ground due to the fact that as the chassis frame moves out from beneath the base frame the springs located above the rear axle of the vehicle are freed of load and lift the vehicle. This means that in order to subsequently re-mount the base frame, or another similar base frame, the base frame must be raised to a corresponding level. Also, the mounting of the legs themselves has proved to be difficult in the prior art.